The GME topology describes a microporous molecular sieve having 1D 12-membered ring (MR) channels intersected by 8 MR channels in 2 dimensions. Its 3D channel (12×8×8) system with pore sizes of 7.11×7.11 Å (12MR) and 3.41×3.41 Å (8MR), respectively, can include spheres up to 7.76 Å. This framework was first recognized in the natural occurring aluminosilicate (zeolite) mineral gmelinite. Since then, routes towards synthetic GME have been explored. Two notable paths are known from the literature: one using cationic (DABCO) polymeric templates in conjunction with a silica sol and sodium aluminate as respective Si and Al sources, and one based on the hydrothermal conversion of zeolite Y (FAU) in presence of Sr2+ cations. However, most materials, and especially the natural occurring gmelinite, are faulted (containing crystallographic errors in the structure, possible causing obstructions of channels etc.) and therefore possess rather low sorption capacities. When exchanged with sodium, nitrogen adsorption capacities, as measured by N2-physisorption at −196° C., were reported to be nearly 0 cm3·g−1 for natural Na-GME and respectively 0.055 cm3·g−1 and 0.031 cm3·g−1 for the DABCO-GME and the GME made by converting FAU. This, together with streaking in electron diffraction indicated that these samples are all highly faulted. It is moreover known that this can be caused by an intergrowth of chabazite (framework topology CHA). The degree of faulting (although present in lesser extent in the DABCO-GME) largely determines the sorption capacity as it blocks the large 12MR channels.
It would be desirable to find a synthetic route to GME with an organic structure directing agent (SDA), that prevents CHA intergrowth and stacking faults and in general, it would be desirable to find a route with a simpler SDA, as the ‘polymeric DABCO’ OSDA is hard to obtain. It would be also be beneficial to find a synthetic route towards GME with Si/Al values above 3.5, since this parameter largely influences the sorption and catalytic properties and the (hydrothermal) stability of the framework.
The present invention is directed to addressing at least some of the shortcomings of the existing art.